This question sounds a bit funny as anyone can do it. But yesterday I found a small shortcut to make Windows 7 desktop icons smaller of bigger in a second. You can make them tiny like ants or bigger like rectangles.
"Just press Ctrl and scroll up or down with your mouse on Windows 7 desktop."
Sometimes things are so easy to do and we don't even know them.
I haven't tried it on Windows XP or others as I don't have them.